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Population genetics

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Genetic variation in color among individuals in a population of the Ochre sea stars (Pisaster ochraceus)

Population genetics is the branch of biology that studies the distribution and change in allele frequencies under the influence of the following four processes: natural selection, genetic drift, mutation and gene flow.[1] The population genetics is concerned with the study at the level of an entire population of organisms.[2] To the point of view of population genetics, according to the evolutionary view, the process of evolution consists of a series of gene substitutions.[3]

Concepts

Population

Main article: Population

A population is a group of individuals pertaining to the same species living in a defined geographical area and effectively or potentially interbreed.[4]

Gene pool

Gene pool is the full set of alleles which can be found in the genetic material of each of living individuals of given population or, in other words, is the totally of the genes of a given sexual population. [5][6]

The four processes

Natural selection

Main article: Natural selection

Natural selection is also known as the survival of the fittest. It is an observable effect of nature and is considered a verifiable mechanism responsible for biological evolution. Natural selection does not create new traits in organisms: it only favors the spreading of advantageous pre-existing traits, and disfavors the spreading of disadvantageous pre-existing traits. In other words, selection is the inbreeding of favored genes, which reduces the diversity of genetic information in a population, and (in the absence of some other source for genetic diversity to outpace selection) produces a purebreed or genetic homozygote for the trait in question. The result is that organisms become highly tailored to their environment over time, and harmful mutations are kept from spreading throughout the population.

Genetic drift

Main article: Genetic drift

Genetic drift is the establishment of certain alleles due to random sampling of the gene pool.[7] Genetic drift refers to the net decrease in genetic variability and heterozygosity over time. In stable populations, genetic drift causes genetic variation to decrease significantly more quickly than mutation can add new variation. Genetic Drift is a stocastic or random genetic process.[8]

Mutation

Main article: Mutation

A mutation is any spontaneous heritable change in DNA sequence that contributes to genetic variability.

Gene flow

Main article: Gene flow

Gene flow is the transfer of alleles or genes from one population to another. In other definition, is the propagation of genes from one breeding population to another by migration, possibly leading to changes in allele frequency. The overall effect of gene flow is that it hinders the genetic divergence between populations and increases the genetic variation within populations.[9]

History

Even before the science of genetics was born the inheritance of quantitative characters has been the subject of intense research.[10] Subsequently it was the work of the British biologist Ronald A. Fisher starting in 1918 that provided a theoretical basis for the inheritance of quantitative characters.[10] Along with Fisher and the American biologist Sewall Wright, the British geneticist J.B.S. Haldane was one of the three founders of the field of study of population genetics.[11]

References

  1. Gillespie, John H (1998). Population Genetics: A Concise Guide. Baltimore/London: The John Hopkins University Press. p. 19-48. ISBN 0-8018-5755-4. 
  2. Snustad, Peter; Simmons, Michael J (2012). Principles of Genetics (6th ed.). River Street, Hoboken, NJ: John Wiley & Sons, Inc. p. 12. ISBN 978-0-470-90359-9. 
  3. Kimura, Motoo; Ohta, Tomoko (1971). Theoretical Aspects of Population Genetics. Princeton, New Jersey: Princeton University Press. p. 16. ISBN 0-691-08098-4. 
  4. Klug, William S.; Cummings, Michael R.; Spencer, Charlotte A.; Palladino, Michael A (2012). Concepts of Genetics (10th ed.). Boston: Pearson. p. 698. ISBN 978-0-321-72412-0. 
  5. Futuyma, Douglas J. (2005). Evolution. Sunderland, Massachusetts: Sinauer Associates, Inc. p. 548. ISBN 978-0-87893-187-3. 
  6. Meyer, Stephen C.; Nelson, Paul A.; Moneymaker, Jonathan; Minnich, Scott; Seelke, Ralph (2009). Explore Evolution: The Arguments For and Against Neo-Darwinism. Malvern, Victoria: Hill House Publishers. p. 146. ISBN 978-0-947352-41-6. 
  7. Lester, Lane P; Bohlin, Raymond G (1989). The Natural Limits to Biological Change (2nd ed.). Dallas: Probe Books. ISBN 0-945241-06-2. 
  8. Dobzhansky, Theodosius (1973). Genetic Diversity & Human Equality:The Facts & Fallacies in the Explosive Genetics & Education Controversy. New York: Basic Books. p. 78. ISBN 0-465-09710-3. 
  9. Pierce, Benjamin (2003). Genetics: A Conceptual Approach. W. H. Freeman. p. 681. ISBN 978-1-57259160-8. 
  10. 10.0 10.1 Narain, P (1993). "Population Genetics of Quantitative Characters". In Majumder, Partha P. Human Population Genetics: A Centennial Tribute to J.B.S.Hadane. London: Plenum Press. p. 31. ISBN 0-306-44572-7. 
  11. Batten, Don (2005). "Haldane's Dilemma Has Not Been Solved". TJ The In-depth Journal of Creation 19 (1): 20-21. ISSN 1036-2916.